import math
def main(arr):
    n=len(arr)
    prefix=[0]*n
    suffix=[0]*n
    
    ps={-1:0}
    curr=0
    for i in range(n):
        x=arr[i]
        curr+=x
        ps[i]=curr
    
    prefix_maxi=-math.inf
    for ij in range(n):
        prefix_maxi=max(prefix_maxi,ps[ij])
        prefix[ij]=prefix_maxi
    
    suffix_maxi=-math.inf
    for jk in range(n-1,-1,-1):
        suffix_maxi=max(suffix_maxi,ps[jk])
        suffix[jk]=suffix_maxi
        
    
    maxAns=-math.inf
    for j in range(n):
        maxAns=max(maxAns,prefix[j] - ps[j] + suffix[j])
    
    return 2*maxAns - ps[n-1]
    
    
print(main([-3,4,-5,2,6,-5]))